The purpose of this work is to determine the parameters of spontaneous-thought-intrusions (daydreaming) and related mental activity such as insight, intuition, mindwandering, and curiosity. This is accomplished through the use of retrospective questionnaires and experimental manipulation. Topics of present interest are: (a) the lifespan changes in daydreaming in a longitudinal sample, (b) the relation of sexual daydreaming and sexual activity to the menopause, (c) the relation of daydreaming incidence to tasks of varing vigilance requirements, and (d) the dimensions of ongoing thoughts on a lifespan sample.